TY - JOUR A1 - Kühn, Nicolas M. A1 - Scherbaum, Frank A1 - Riggelsen, Carsten T1 - Deriving empirical ground-motion models : balancing data constraints and physical assumptions to optimize prediction capability N2 - Empirical ground-motion models used in seismic hazard analysis are commonly derived by regression of observed ground motions against a chosen set of predictor variables. Commonly, the model building process is based on residual analysis and/or expert knowledge and/or opinion, while the quality of the model is assessed by the goodness-of-fit to the data. Such an approach, however, bears no immediate relation to the predictive power of the model and with increasing complexity of the models is increasingly susceptible to the danger of overfitting. Here, a different, primarily data-driven method for the development of ground-motion models is proposed that makes use of the notion of generalization error to counteract the problem of overfitting. Generalization error directly estimates the average prediction error on data not used for the model generation and, thus, is a good criterion to assess the predictive capabilities of a model. The approach taken here makes only few a priori assumptions. At first, peak ground acceleration and response spectrum values are modeled by flexible, nonphysical functions (polynomials) of the predictor variables. The inclusion of a particular predictor and the order of the polynomials are based on minimizing generalization error. The approach is illustrated for the next generation of ground-motion attenuation dataset. The resulting model is rather complex, comprising 48 parameters, but has considerably lower generalization error than functional forms commonly used in ground-motion models. The model parameters have no physical meaning, but a visual interpretation is possible and can reveal relevant characteristics of the data, for example, the Moho bounce in the distance scaling. In a second step, the regression model is approximated by an equivalent stochastic model, making it physically interpretable. The resulting resolvable stochastic model parameters are comparable to published models for western North America. In general, for large datasets generalization error minimization provides a viable method for the development of empirical ground-motion models. Y1 - 2009 UR - http://bssa.geoscienceworld.org/ U6 - https://doi.org/10.1785/0120080136 SN - 0037-1106 ER - TY - JOUR A1 - Delavaud, Elise A1 - Scherbaum, Frank A1 - Kuehn, Nicolas A1 - Riggelsen, Carsten T1 - Information-theoretic selection of ground-motion prediction equations for seismic hazard analysis : an applicability study using Californian data N2 - Considering the increasing number and complexity of ground-motion prediction equations available for seismic hazard assessment, there is a definite need for an efficient, quantitative, and robust method to select and rank these models for a particular region of interest. In a recent article, Scherbaum et al. (2009) have suggested an information- theoretic approach for this purpose that overcomes several shortcomings of earlier attempts at using data-driven ground- motion prediction equation selection procedures. The results of their theoretical study provides evidence that in addition to observed response spectra, macroseismic intensity data might be useful for model selection and ranking. We present here an applicability study for this approach using response spectra and macroseismic intensities from eight Californian earthquakes. A total of 17 ground-motion prediction equations, from different regions, for response spectra, combined with the equation of Atkinson and Kaka (2007) for macroseismic intensities are tested for their relative performance. The resulting data-driven rankings show that the models that best estimate ground motion in California are, as one would expect, Californian and western U. S. models, while some European models also perform fairly well. Moreover, the model performance appears to be strongly dependent on both distance and frequency. The relative information of intensity versus response spectral data is also explored. The strong correlation we obtain between intensity-based rankings and spectral-based ones demonstrates the great potential of macroseismic intensities data for model selection in the context of seismic hazard assessment. Y1 - 2009 UR - http://bssa.geoscienceworld.org/ U6 - https://doi.org/10.1785/0120090055 SN - 0037-1106 ER - TY - JOUR A1 - Faenza, Licia A1 - Hainzl, Sebastian A1 - Scherbaum, Frank T1 - Statistical analysis of the Central-Europe seismicity N2 - The aim of this paper is to characterize the spatio-temporal distribution of Central-Europe seismicity. Specifically, by using a non-parametric statistical approach, the proportional hazard model, leading to an empirical estimation of the hazard function, we provide some constrains on the time behavior of earthquake generation mechanisms. The results indicate that the most conspicuous characteristics of M-w 4.0+ earthquakes is a temporal clustering lasting a couple of years. This suggests that the probability of occurrence increases immediately after a previous event. After a few years, the process becomes almost time independent. Furthermore, we investigate the cluster properties of the seismicity of Central-Europe, by comparing the obtained result with the one of synthetic catalogs generated by the epidemic type aftershock sequences (ETAS) model, which previously have been successfully applied for short term clustering. Our results indicate that the ETAS is not well suited to describe the seismicity as a whole, while it is able to capture the features of the short- term behaviour. Remarkably, similar results have been previously found for Italy using a higher magnitude threshold. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00401951 U6 - https://doi.org/10.1016/j.tecto.2008.04.030 SN - 0040-1951 ER - TY - JOUR A1 - Wassermann, Joachim A1 - Ohrnberger, Matthias A1 - Scherbaum, Frank A1 - Gossler, J. A1 - Zschau, Jochen T1 - Kontinuierliche seismologische Netz- und Arraymessungen am Dekadenvulkan Merapi (Java, Indonesien) : ein Zwischenresümee = Continuous measurements at Merapi volcano (Java, Indonesia) using anetwork of small-scale seismograph arrays Y1 - 1998 SN - 0947-1944 ER - TY - JOUR A1 - Koehler, Andreas A1 - Ohrnberger, Matthias A1 - Scherbaum, Frank T1 - Unsupervised feature selection and general pattern discovery using Self-Organizing Maps for gaining insights into the nature of seismic wavefields N2 - This study presents an unsupervised feature selection and learning approach for the discovery and intuitive imaging of significant temporal patterns in seismic single-station or network recordings. For this purpose, the data are parametrized by real-valued feature vectors for short time windows using standard analysis tools for seismic data, such as frequency-wavenumber, polarization, and spectral analysis. We use Self-Organizing Maps (SOMs) for a data-driven feature selection, visualization and clustering procedure, which is in particular suitable for high-dimensional data sets. Our feature selection method is based on significance testing using the Wald-Wolfowitz runs test for-individual features and on correlation hunting with SOMs in feature subsets. Using synthetics composed of Rayleigh and Love waves and real-world data, we show the robustness and the improved discriminative power of that approach compared to feature subsets manually selected from individual wavefield parametrization methods. Furthermore, the capability of the clustering and visualization techniques to investigate the discrimination of wave phases is shown by means of synthetic waveforms and regional earthquake recordings. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00983004 U6 - https://doi.org/10.1016/j.cageo.2009.02.004 SN - 0098-3004 ER - TY - JOUR A1 - Runge, Antonia K. A1 - Scherbaum, Frank A1 - Curtis, Andrew A1 - Riggelsen, Carsten T1 - An interactive tool for the elicitation of subjective probabilities in probabilistic seismic-hazard analysis JF - Bulletin of the Seismological Society of America N2 - In probabilistic seismic-hazard analysis, epistemic uncertainties are commonly treated within a logic-tree framework in which the branch weights express the degree of belief of an expert in a set of models. For the calculation of the distribution of hazard curves, these branch weights represent subjective probabilities. A major challenge for experts is to provide logically consistent weight estimates (in the sense of Kolmogorovs axioms), to be aware of the multitude of heuristics, and to minimize the biases which affect human judgment under uncertainty. We introduce a platform-independent, interactive program enabling us to quantify, elicit, and transfer expert knowledge into a set of subjective probabilities by applying experimental design theory, following the approach of Curtis and Wood (2004). Instead of determining the set of probabilities for all models in a single step, the computer-driven elicitation process is performed as a sequence of evaluations of relative weights for small subsets of models. From these, the probabilities for the whole model set are determined as a solution of an optimization problem. The result of this process is a set of logically consistent probabilities together with a measure of confidence determined from the amount of conflicting information which is provided by the expert during the relative weighting process. We experiment with different scenarios simulating likely expert behaviors in the context of knowledge elicitation and show the impact this has on the results. The overall aim is to provide a smart elicitation technique, and our findings serve as a guide for practical applications. Y1 - 2013 U6 - https://doi.org/10.1785/0120130026 SN - 0037-1106 SN - 1943-3573 VL - 103 IS - 5 SP - 2862 EP - 2874 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Scherbaum, Frank A1 - Bouin, M. P. T1 - FIR filter effects and nucleation phases Y1 - 1997 ER - TY - JOUR A1 - Scherbaum, Frank T1 - Zero Phase FIR filters in digital seismic acquisition systems : blessing or curse Y1 - 1997 ER - TY - JOUR A1 - Scherbaum, Frank A1 - Delavaud, Elise A1 - Riggelsen, Carsten T1 - Model selection in seismic hazard analysis : an information-theoretic perspective N2 - Although the methodological framework of probabilistic seismic hazard analysis is well established, the selection of models to predict the ground motion at the sites of interest remains a major challenge. Information theory provides a powerful theoretical framework that can guide this selection process in a consistent way. From an information- theoretic perspective, the appropriateness of models can be expressed in terms of their relative information loss (Kullback-Leibler distance) and hence in physically meaningful units (bits). In contrast to hypothesis testing, information-theoretic model selection does not require ad hoc decisions regarding significance levels nor does it require the models to be mutually exclusive and collectively exhaustive. The key ingredient, the Kullback-Leibler distance, can be estimated from the statistical expectation of log-likelihoods of observations for the models under consideration. In the present study, data-driven ground-motion model selection based on Kullback-Leibler-distance differences is illustrated for a set of simulated observations of response spectra and macroseismic intensities. Information theory allows for a unified treatment of both quantities. The application of Kullback-Leibler-distance based model selection to real data using the model generating data set for the Abrahamson and Silva (1997) ground-motion model demonstrates the superior performance of the information-theoretic perspective in comparison to earlier attempts at data- driven model selection (e.g., Scherbaum et al., 2004). Y1 - 2009 UR - http://bssa.geoscienceworld.org/ U6 - https://doi.org/10.1785/0120080347 SN - 0037-1106 ER - TY - JOUR A1 - Rietbrock, Andreas A1 - Scherbaum, Frank T1 - Crustal scattering at the KTB from a combined microearthquake and receiver analysis Y1 - 1998 ER - TY - JOUR A1 - Rietbrock, Andreas A1 - Scherbaum, Frank T1 - The GIANT analysis system (Graphical Interaktive Aftershock Network Toolbox) Y1 - 1998 ER - TY - JOUR A1 - Bommer, Julian J. A1 - Coppersmith, Kevin J. A1 - Coppersmith, Ryan T. A1 - Hanson, Kathryn L. A1 - Mangongolo, Azangi A1 - Neveling, Johann A1 - Rathje, Ellen M. A1 - Rodriguez-Marek, Adrian A1 - Scherbaum, Frank A1 - Shelembe, Refilwe A1 - Stafford, Peter J. A1 - Strasser, Fleur O. T1 - A SSHAC Level 3 Probabilistic Seismic Hazard Analysis for a New-Build Nuclear Site in South Africa JF - Earthquake spectra : the professional journal of the Earthquake Engineering Research Institute N2 - A probabilistic seismic hazard analysis has been conducted for a potential nuclear power plant site on the coast of South Africa, a country of low-to-moderate seismicity. The hazard study was conducted as a SSHAC Level 3 process, the first application of this approach outside North America. Extensive geological investigations identified five fault sources with a non-zero probability of being seismogenic. Five area sources were defined for distributed seismicity, the least active being the host zone for which the low recurrence rates for earthquakes were substantiated through investigations of historical seismicity. Empirical ground-motion prediction equations were adjusted to a horizon within the bedrock at the site using kappa values inferred from weak-motion analyses. These adjusted models were then scaled to create new equations capturing the range of epistemic uncertainty in this region with no strong motion recordings. Surface motions were obtained by convolving the bedrock motions with site amplification functions calculated using measured shear-wave velocity profiles. Y1 - 2015 U6 - https://doi.org/10.1193/060913EQS145M SN - 8755-2930 SN - 1944-8201 VL - 31 IS - 2 SP - 661 EP - 698 PB - Earthquake Engineering Research Institute CY - Oakland ER - TY - JOUR A1 - Hiemer, Stefan A1 - Rößler, Dirk A1 - Scherbaum, Frank T1 - Monitoring the West Bohemian earthquake swarm in 2008/2009 by a temporary small-aperture seismic array JF - Journal of seismology N2 - The most recent intense earthquake swarm in West Bohemia lasted from 6 October 2008 to January 2009. Starting 12 days after the onset, the University of Potsdam monitored the swarm by a temporary small-aperture seismic array at 10 km epicentral distance. The purpose of the installation was a complete monitoring of the swarm including micro-earthquakes (M (L) < 0). We identify earthquakes using a conventional short-term average/long-term average trigger combined with sliding-window frequency-wavenumber and polarisation analyses. The resulting earthquake catalogue consists of 14,530 earthquakes between 19 October 2008 and 18 March 2009 with magnitudes in the range of -aEuro parts per thousand 1.2 a parts per thousand currency signaEuro parts per thousand M (L) a parts per thousand currency signaEuro parts per thousand 2.7. The small-aperture seismic array substantially lowers the detection threshold to about M (c) = -aEuro parts per thousand 0.4, when compared to the regional networks operating in West Bohemia (M (c) > 0.0). In the course of this work, the main temporal features (frequency-magnitude distribution, propagation of back azimuth and horizontal slowness, occurrence rate of aftershock sequences and interevent-time distribution) of the recent 2008/2009 earthquake swarm are presented and discussed. Temporal changes of the coefficient of variation (based on interevent times) suggest that the swarm earthquake activity of the 2008/2009 swarm terminates by 12 January 2009. During the main phase in our studied swarm period after 19 October, the b value of the Gutenberg-Richter relation decreases from 1.2 to 0.8. This trend is also reflected in the power-law behavior of the seismic moment release. The corresponding total seismic moment release of 1.02x10(17) Nm is equivalent to M (L,max) = 5.4. KW - Swarm earthquakes KW - West Bohemia KW - Array seismology KW - Frequency-magnitude distribution Y1 - 2012 U6 - https://doi.org/10.1007/s10950-011-9256-5 SN - 1383-4649 VL - 16 IS - 2 SP - 169 EP - 182 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Delavaud, Elise A1 - Scherbaum, Frank A1 - Kühn, Nicolas A1 - Allen, Trevor T1 - Testing the global applicability of ground-motion prediction equations for active shallow crustal regions JF - Bulletin of the Seismological Society of America N2 - Large research initiatives such as the Global Earthquake Model (GEM) or the Seismic HAzard haRmonization in Europe (SHARE) projects concentrate a great collaborative effort on defining a global standard for seismic hazard estimations. In this context, there is an increasing need for identifying ground-motion prediction equations (GMPEs) that can be applied at both global and regional scale. With increasing amounts of strong-motion records that are now available worldwide, observational data can provide a valuable resource to tackle this question. Using the global dataset of Allen and Wald (2009), we evaluate the ability of 11 GMPEs to predict ground-motion in different active shallow crustal regions worldwide. Adopting the approach of Scherbaum et al. (2009), we rank these GMPEs according to their likelihood of having generated the data. In particular, we estimate how strongly data support or reject the models with respect to the state of noninformativeness defined by a uniform weighting. Such rankings derived from this particular global dataset enable us to explore the potential of GMPEs to predict ground motions in their host region and also in other regions depending on the magnitude and distance considered. In the ranking process, we particularly focus on the influence of the distribution of the testing dataset compared with the GMPE's native dataset. One of the results of this study is that some nonindigenous models present a high degree of consistency with the data from a target region. Two models in particular demonstrated a strong power of geographically wide applicability in different geographic regions with respect to the testing dataset: the models of Akkar and Bommer (2010) and Chiou et al. (2010). Y1 - 2012 U6 - https://doi.org/10.1785/0120110113 SN - 0037-1106 VL - 102 IS - 2 SP - 707 EP - 721 PB - Seismological Society of America CY - El Cerrito ER - TY - JOUR A1 - Haney, Frank A1 - Kummerow, J. A1 - Langenbruch, C. A1 - Dinske, C. A1 - Shapiro, Serge A. A1 - Scherbaum, Frank T1 - Magnitude estimation for microseismicity induced during the KTB 2004/2005 injection experiment JF - Geophysics N2 - We determined the magnitudes of 2540 microseismic events measured at one single 3C borehole geophone at the German Deep Drilling Site (known by the German acronym, KTB) during the injection phase 2004/2005. For this task we developed a three-step approach. First, we estimated local magnitudes of 104 larger events with a standard method based on amplitude measurements at near-surface stations. Second, we investigated a series of parameters to characterize the size of these events using the seismograms of the borehole sensor, and we compared them statistically with the local magnitudes. Third, we extrapolated the regression curve to obtain the magnitudes of 2436 events that were only measured at the borehole geophone. This method improved the magnitude of completeness for the KTB data set by more than one order down to M = -2.75. The resulting b-value for all events was 0.78, which is similar to the b-value obtained from taking only the greater events with standard local magnitude estimation from near-surface stations, b = 0.86. The more complete magnitude catalog was required to study the magnitude distribution with time and to characterize the seismotectonic state of the KTB injection site. The event distribution with time was consistent with prediction from theory assuming pore pressure diffusion as the underlying mechanism to trigger the events. The value we obtained for the seismogenic index of -4 suggested that the seismic hazard potential at the KTB site is comparatively low. Y1 - 2011 U6 - https://doi.org/10.1190/GEO2011-0020.1 SN - 0016-8033 VL - 76 IS - 6 SP - WC47 EP - WC53 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - JOUR A1 - Hiemer, Stefan A1 - Scherbaum, Frank A1 - Rößler, Dirk A1 - Kühn, Nicolas T1 - Determination of tau(0) and Rock Site kappa from Records of the 2008/2009 Earthquake Swarm in Western Bohemia JF - Seismological research letters Y1 - 2011 U6 - https://doi.org/10.1785/gssrl.82.3.387 SN - 0895-0695 VL - 82 IS - 3 SP - 387 EP - 393 PB - Seismological Society of America CY - El Cerrito ER - TY - JOUR A1 - Gianniotis, Nikolaos A1 - Kuehn, Nicolas A1 - Scherbaum, Frank T1 - Manifold aligned ground motion prediction equations for regional datasets JF - Computers & geosciences : an international journal devoted to the publication of papers on all aspects of geocomputation and to the distribution of computer programs and test data sets ; an official journal of the International Association for Mathematical Geology N2 - Inferring a ground-motion prediction equation (GMPE) for a region in which only a small number of seismic events has been observed is a challenging task. A response to this data scarcity is to utilise data from other regions in the hope that there exist common patterns in the generation of ground motion that can contribute to the development of a GMPE for the region in question. This is not an unreasonable course of action since we expect regional GMPEs to be related to each other. In this work we model this relatedness by assuming that the regional GMPEs occupy a common low-dimensional manifold in the space of all possible GMPEs. As a consequence, the GMPEs are fitted in a joint manner and not independent of each other, borrowing predictive strength from each other's regional datasets. Experimentation on a real dataset shows that the manifold assumption displays better predictive performance over fitting regional GMPEs independent of each other. (C) 2014 Elsevier Ltd. All rights reserved. KW - Ground-motion-model KW - Bagging KW - Ensembles KW - Manifold KW - Regional-dependence Y1 - 2014 U6 - https://doi.org/10.1016/j.cageo.2014.04.014 SN - 0098-3004 SN - 1873-7803 VL - 69 SP - 72 EP - 77 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Kühn, Nico M. A1 - Scherbaum, Frank T1 - Ground-motion prediction model building: a multilevel approach JF - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering N2 - A Bayesian ground-motion model is presented that directly estimates the coefficients of the model and the correlation between different ground-motion parameters of interest. The model is developed as a multi-level model with levels for earthquake, station and record terms. This separation allows to estimate residuals for each level and thus the estimation of the associated aleatory variability. In particular, the usually estimated within-event variability is split into a between-station and between-record variability. In addition, the covariance structure between different ground-motion parameters of interest is estimated for each level, i.e. directly the between-event, between-station and between-record correlation coefficients are available. All parameters of the model are estimated via Bayesian inference, which allows to assess their epistemic uncertainty in a principled way. The model is developed using a recently compiled European strong-motion database. The target variables are peak ground velocity, peak ground acceleration and spectral acceleration at eight oscillator periods. The model performs well with respect to its residuals, and is similar to other ground-motion models using the same underlying database. The correlation coefficients are similar to those estimated for other parts of the world, with nearby periods having a high correlation. The between-station, between-event and between-record correlations follow generally a similar trend. KW - Ground-motion prediction equation KW - Probabilistic seismic hazard analysis and Bayesian inference KW - Multilevel model KW - Correlation KW - Single-station sigma Y1 - 2015 U6 - https://doi.org/10.1007/s10518-015-9732-3 SN - 1570-761X SN - 1573-1456 VL - 13 IS - 9 SP - 2481 EP - 2491 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Kühn, Nicolas M. A1 - Riggelsen, Carsten A1 - Scherbaum, Frank T1 - Modeling the joint probability of earthquake, site, and ground-motion parameters using bayesian networks JF - Bulletin of the Seismological Society of America N2 - Bayesian networks are a powerful and increasingly popular tool for reasoning under uncertainty, offering intuitive insight into (probabilistic) data-generating processes. They have been successfully applied to many different fields, including bioinformatics. In this paper, Bayesian networks are used to model the joint-probability distribution of selected earthquake, site, and ground-motion parameters. This provides a probabilistic representation of the independencies and dependencies between these variables. In particular, contrary to classical regression, Bayesian networks do not distinguish between target and predictors, treating each variable as random variable. The capability of Bayesian networks to model the ground-motion domain in probabilistic seismic hazard analysis is shown for a generic situation. A Bayesian network is learned based on a subset of the Next Generation Attenuation (NGA) dataset, using 3342 records from 154 earthquakes. Because no prior assumptions about dependencies between particular parameters are made, the learned network displays the most probable model given the data. The learned network shows that the ground-motion parameter (horizontal peak ground acceleration, PGA) is directly connected only to the moment magnitude, Joyner-Boore distance, fault mechanism, source-to-site azimuth, and depth to a shear-wave horizon of 2: 5 km/s (Z2.5). In particular, the effect of V-S30 is mediated by Z2.5. Comparisons of the PGA distributions based on the Bayesian networks with the NGA model of Boore and Atkinson (2008) show a reasonable agreement in ranges of good data coverage. Y1 - 2011 U6 - https://doi.org/10.1785/0120100080 SN - 0037-1106 VL - 101 IS - 1 SP - 235 EP - 249 PB - Seismological Society of America CY - El Cerrito ER - TY - JOUR A1 - Tran Thanh Tuan, A1 - Scherbaum, Frank A1 - Malischewsky, Peter G. T1 - On the relationship of peaks and troughs of the ellipticity (H/V) of Rayleigh waves and the transmission response of single layer over half-space models JF - Geophysical journal international N2 - One of the key challenges in the context of local site effect studies is the determination of frequencies where the shakeability of the ground is enhanced. In this context, the H/V technique has become increasingly popular and peak frequencies of H/V spectral ratio are sometimes interpreted as resonance frequencies of the transmission response. In the present study, assuming that Rayleigh surface wave is dominant in H/V spectral ratio, we analyse theoretically under which conditions this may be justified and when not. We focus on 'layer over half-space' models which, although seemingly simple, capture many aspects of local site effects in real sedimentary structures. Our starting point is the ellipticity of Rayleigh waves. We use the exact formula of the H/V-ratio presented by Malischewsky & Scherbaum (2004) to investigate the main characteristics of peak and trough frequencies. We present a simple formula illustrating if and where H/V-ratio curves have sharp peaks in dependence of model parameters. In addition, we have constructed a map, which demonstrates the relation between the H/V-peak frequency and the peak frequency of the transmission response in the domain of the layer's Poisson ratio and the impedance contrast. Finally, we have derived maps showing the relationship between the H/V-peak and trough frequency and key parameters of the model such as impedance contrast. These maps are seen as diagnostic tools, which can help to guide the interpretation of H/V spectral ratio diagrams in the context of site effect studies. KW - Site effects KW - Theoretical seismology KW - Wave propagation Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-246X.2010.04863.x SN - 0956-540X VL - 184 IS - 2 SP - 793 EP - 800 PB - Wiley-Blackwell CY - Malden ER -